David C. Sheridan

North Carolina State University, Raleigh, North Carolina, United States

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Publications (59)17.9 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The short-circuit reliability of power switches plays very important part in many applications, where a 10μs short-circuit duration at 400V is usually required for 650V switches. Although emerging high voltage AlGaN/GaN HEMT technologies have shown switching advantages, the short-circuit performance has not been thoroughly investigated. In this work, we present an experimental study and numerical simulation analysis of 650V AlGaN/GaN HEMTs short-circuit safe-operating-area (SCSOA), and provide a theory for the reduction in ruggedness at high voltage short circuit conditions.
    No preview · Conference Paper · Jun 2014
  • D.C. Sheridan · D.Y. Lee · A. Ritenour · V. Bondarenko · J. Yang · C. Coleman
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    ABSTRACT: An emerging generation of high voltage (600V - 1200V) GaN HEMTs are compared to the best in class existing technologies and are shown to maintain a significant advantage in switching performance. Compared to the latest available GaN and Si superjunction MOSFET at 650V, these GaN devices show > 5X lower switching energies with an Ron*Qg product less than 1 nC *Ω. These GaN devices are extended to show > 1200V breakdown voltages and have switching losses 4X lower than even SiC MOSFETs with similar ratings.
    No preview · Article · Jan 2014
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    ABSTRACT: The fast switching speeds, large current handling capability and superior thermal properties of SiC makes SiC Vertical Trench JFETs (VJFETs) ideal candidates for power electronic applications. This paper reports on the recent progress in the development of a low resistance 1200V/25mOhm EM VJFET and a new range of DM JFETs with ratings from 650V to 1700V, and resistances below 22mOhms. The lowest rated voltage class of VJFET, the 650V/55mOhm DM VJFET designed for use in 600-800V applications, has a breakdown voltage of 900V and R-DSON,R-SP of 1.46mOhm-cm(2). This RDSON, SP is the lowest reported value for a VJFET and is an order of magnitude lower compared to the best Si Super Junction (SJ) MOSFETs reported in the literature.
    No preview · Article · Mar 2013 · ECS Transactions
  • D.C. Sheridan · K. Chatty · V. Bondarenko · J.B. Casady
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    ABSTRACT: 1200V SiC vertical trench JFETs have been evaluated for their reverse conduction properties. Absent of a traditional body diode, the SiC trench JFET is shown to be able to operate effectively in reverse mode when used with or without an antiparallel diode in applications requiring reverse commutation. Device characteristics and experimental results are given for both traditional half-bridge and cascode topologies.
    No preview · Conference Paper · Jan 2012
  • Source
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    ABSTRACT: A novel SiC junction field-effect transistor (JFET) model that uses a unified description of linear and saturated conduction modes is proposed. Advantages of the proposed model are improved robustness and convergence, inclusion of field-dependent mobility effects, and more physical description of the current saturation phenomenon. The model is validated against a normally off JFET sample over a wide temperature range. Finite-element simulations are used to demonstrate the physics-based nature of the proposed model.
    Preview · Article · Sep 2011 · IEEE Transactions on Industry Applications
  • Source
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    ABSTRACT: A practical parameter extraction procedure for a power silicon carbide (SiC) junction field-effect transistor (JFET) is presented. The carrier mobility and carrier concentration are very important parameters, strongly affecting the device current capability and dynamic characteristics for a given design. When modeling JFETs, the values of these parameters are usually based on assumptions and given by a vendor in a range. As a result, model accuracy is compromised. In this paper, a step-by-step parameter extraction procedure is described that includes the extraction of mobility and carrier concentration in the channel and drift regions based on knowledge of device geometrical parameters. For the first time, carrier mobilities in the channel and drift regions of a power JFET are extracted individually. It is found that channel and drift region mobilities can be very different for a given device since they are strongly dependent on the fabrication process. The separate extraction of these two mobilities can also improve model accuracy in the case of imperfect knowledge of the device geometry. The developed procedure includes the extraction of empirical parameters describing the temperature dependence of mobilities in the channel and drift regions. A simple static I - V characterization and C - V measurements are the only measurements required for the parameter extraction. In this paper, the procedure is experimentally validated for both normally off (enhancement mode) and normally on (depletion mode) JFETs.
    Preview · Article · Sep 2011 · IEEE Transactions on Industry Applications
  • D. Sheridan · J. Casady · M. Mazzola · R. Schrader · V. Bondarenko
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    ABSTRACT: The SiC Junction Field Effect Transistor (JFET) technology has continued to mature, allowing for a wider range of product offerings that are expected to play an important role in the future aerospace and hybrid vehicle system designs. This paper will give an overview of vertical trench SiC JFET technology detailing the high-temperature dc characteristics of the discrete devices also show power module switching behavior up to 100A. Additional characterization of the all-SiC power modules used as solid-state circuit breakers will be given.
    No preview · Article · Jan 2011
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    ABSTRACT: Silicon Carbide (SiC) is an emerging semiconductor material which has been widely predicted to be superior to both Si and GaAs in the area of power electronic switching devices [1]. This paper presents an overview of SiC power devices and concludes that MOS Turn-Off Thyristor (MTOTM) is one of the most promising near term SiC switching device given its high power potential, ease of turn-off, 500°C operation and resulting reduction in cooling requirements. It is further concluded that in order to take advantage of SiC power devices, high temperature packages and components with double sided attachment need to be developed along with the SiC power devices.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • R. Schrader · K. Speer · J. Casady · V. Bondarenko · D. Sheridan
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    ABSTRACT: The high-temperature static and dynamic characteristics of the new 1200 V, 45 mΩ, 9 mm2 depletion-mode SiC vertical trench junction field-effect transistor (vtJFET) are compared with those of a 1200 V, 50 mΩ, 9 mm2 enhancement-mode SiC vtJFET. It is shown that both devices are fully capable of high-temperature operation and that each type has its own unique advantages. For applications operating in extreme high-temperature environments, the larger saturation current (∼2.5x) and lower on-state resistance (∼150 mΩ at 250 °C) of the depletion-mode SiC vtJFET provide very attractive performance at temperatures beyond silicon's fundamental limitations. In addition, operating the normally-on vtJFET at VGS less than 2 V reduces the gate drive's current requirements to a negligible level, which is an important design factor for high-temperature power modules that use multiple die in parallel.
    No preview · Article · Jan 2011
  • J. B. Casady · D. C. Sheridan · W. C. Dillard · R. W. Johnson
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    ABSTRACT: Discrete, buried-gate 4H-SiC JFETs (W/L = 1 mm/5 μm) were packaged and characterized at temperatures ranging from 290 K to 773 K for use in a hybrid, 4H-SiC analog amplifier. A contaminated passivation oxide was found to limit high-temperature operation initially, but upon removal of the passivation layer the devices demonstrated stable operation to 773 K with adequate amplification (Av greater than 200 V/V) up to 673 K. From the 16 devices tested, a peak extrinsic saturated transconductance (gmsa) of 27.1 mS/mm was measured at 308 K, corresponding to a channel mobility of 400 cm2/V.s, excluding significant series resistance effects.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • Source
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    ABSTRACT: In this paper, a physical model for a SiC Junction Field Effect Transistor (JFET) is presented. The novel feature of the model is that the mobility dependence on both tempera-ture and electric field is taken into account. This is particularly important for high-current power devices where the maximum conduction current is limited by drift velocity saturation in the channel. The model equations are described in detail, emphasizing the differences introduced by the field-dependent mobility model. The model is then implemented in Pspice. Both static and dynamic simulation results are given. The results are validated with ex-perimental results under static conditions and under resistive and inductive switching conditions. Index Terms—Field-dependent mobility, junction field effect transistor (JFET), physics-based model, silicon carbide (SiC).
    Preview · Article · Jan 2011 · IEEE Transactions on Industry Applications
  • D.C. Sheridan · A. Ritenour · R. Kelley · V. Bondarenko · J.B. Casady
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    ABSTRACT: The unique wide bandgap properties of SiC allow the creation of high performance normally-off vertical JFET power device. Due to the vertical nature of the device, it can easily be designed with blocking capability exceeding 2kV with R<sub>DS(ON), sp</sub> > 3mΩ-cm<sup>2</sup>, resulting in the lowest specific on-resistance for enhancement mode SiC devices with V<sub>BR</sub> <; 1200V. The low R<sub>DS(ON), sp</sub> yields a small die size that translates into switching losses that are 5-10X smaller than similarly rated Si IGBTs. When used as an IGBT replacement, a significant reduction in losses can be achieved, greatly increasing the overall system efficiency of solar inverters and other renewable power systems.
    No preview · Conference Paper · Jul 2010
  • A. Ritenour · D.C. Sheridan · V. Bondarenko · J.B. Casady
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    ABSTRACT: Excellent performance and record inverter efficiency have been reported for 1200 V normally-off silicon carbide (SiC) vertical channel junction field effect transistors (VJFETs) with uniform channel doping. Optimally designed normally-off SiC VJFETs typically have a threshold voltage of approximately +1 V and pentode-like output characteristics with clear saturation. Some applications require significant surge or pulsed current capability thus it is desirable to increase saturation current density while maintaining normally-off operation. This paper reports the use of non-uniform channel doping in a normally-off SiC power VJFET to achieve a 28-48% increase in saturation current and 13% decrease in on-resistance compared to the uniform channel case. This results in a specific on-resistance of 2.5 mΩ·cm<sup>2</sup> and saturation current density of 1275 A·cm<sup>-2</sup> at 25°C. Forward drain leakage at V<sub>gs</sub>= 0 V and V<sub>ds</sub>= 1100 V (measurement setup limit) is very similar for both channel doping profiles and remains less than 55 uA (1.75 mA·cm<sup>-2</sup>) at 150°C for the non-uniform channel SiC VJFET. The total switching energy for non-uniform channel devices was 194 μJ compared to 190 μJ for uniform channel devices.
    No preview · Conference Paper · Jul 2010
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    ABSTRACT: A 1200-V, 600-A silicon carbide (SiC) JFET half-bridge module has been developed for drop-in replacement of a 600-V, 600-A IGBT intelligent power module (IPM). Advances in the development of SiC field effect transistors have resulted in reliable high yield devices that can be paralleled and packaged to produce high-voltage and high-current power modules not only competitive with existing IGBT technology but the modules have expanded capabilities. A SiC vertical junction field effect transistor VJFET has been produced with the properties of lower conduction loss, zero tail current, higher thermal conductivity, and higher power density when compared to a similarly rated silicon IGBT or any practical SiC MOSFETs previously reported. Three prototype SiC JFET half-bridge modules with gate drivers have been successfully integrated into a three-phase 30-kW (continuous), 100-kW (intermittent) AC synchronous motor drive designed to control a traction motor in an electric vehicle. The commercially available motor drive, originally designed for silicon IGBT IPMs, was evaluated in conjunction with a permanent-magnet brushless DC motor on a dynamometer. Normal operation of the motor drive using field-oriented control and pulse-width modulation at 12.5 kHz was observed. Characterization of the SiC power module in the forward bias safe operating area demonstrated up to a 50% reduction in forward conduction losses as compared to the silicon IGBT IPM it replaces. The lack of a body diode in the SiC vertical-channel JFET is one major advantage of this switch topology allowing SiC Schottky barrier diodes to be used as the anti-parallel rectifier without undesirable conduction through a MOSFET body diode. Modules have been constructed using both depletion mode and enhancement mode 1200-V VJFET switches with industry leading low specific on resistance (<4 mω-cm 2) produced by SemiSouth Laboratories.
    No preview · Article · Apr 2010 · SAE Technical Papers
  • Andrew Ritenour · David C. Sheridan · Vlad Bondarenko · Jeff B. Casady
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    ABSTRACT: Recently 63 m Omega, 100 m Omega, and 125 m Omega 1200 V normally-off SiC VJFETs have become commercially available and 99% efficiency has been demonstrated in a single-phase solar inverter using these components [1]. They exhibit low specific on-resistance (3 m Omega.cm(2)), high saturation current density (1000 A.cm(-2)), and low switching losses. For some applications, including 30 to 100 kW inverter modules and those requiring high surge current capability, larger die size is required. This paper reports the static and dynamic performance of 15 mm(2) 1200 V normally-off VJFETs with 25 m Omega on-resistance and 120 A saturation current at 25 degrees C.
    No preview · Article · Apr 2010 · Materials Science Forum
  • Robin Kelley · Andrew Ritenour · David Sheridan · Jeff Casady
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    ABSTRACT: Normally-OFF SiC VJFETs have been proved to be advantageous as a ¿drop-in¿ replacement of MOSFETs and IGBTs in a variety of applications. As this device's acceptance continues to grow, developers are investigating optimized driver methods that will yield the best possible switching performance leading to higher system efficiencies. This paper presents new results for an alternative and more optimized gate driver to the capacitive coupled driver used in past literature. Additionally switching energy measurements are documented for the 50 mOhm enhancement-mode SiC VJFET in the newly optimized two-stage, DC-coupled gate driver and compared against past results obtained using the initial driver design. Specific design guidelines are included for achieving the best possible results using the two stage gate driver design presented here.
    No preview · Conference Paper · Mar 2010
  • J.B. Casady · D.C. Sheridan · A. Ritenour · V. Bondarenko · R. Kelley
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    ABSTRACT: Normally-off Silicon Carbide (SiC) power Junction Field Effect Transistors (JFETs) were compared with competing power transistor technology at temperatures from 25 °C to 150 °C as limited by the packaging. Switching energies were measured from 1200 V, 125 mω and 50 mω (room temperature) rated SiC power JFETs and compared with 900 V silicon (Si) super-junction Metal Oxide Semiconductors (MOSFETs) and 1200 V Si Insulated Gate Bipolar Transistors (IGBTs). For both comparisons, measured performance for the SiC power JFET was advantageous at all temperatures when switching at 50 kHz, including a total switching energy (ESW) of 97 μJ for the SiC JFET, compared with 158 μJ for the Si super-junction MOSFET, and 550 μJ for the Si IGBT at 25 °C. At 150°C, the ESW was 138 μJ for the SiC power JFET, 413 μJ for the Si super-junction MOSFET, and 1020 μJ for the Si IGBT. Increasing the die size of the 1200 V, normally-off SiC JFET by 2.25 resulted in an measured increase in switching energy of 2.7 and 2.37 at 25 °C and 150 °C, respectively, a quasi-linear relationship. Higher power preview products of the SiC normally-off JFET technology were also examined including a 1200 V, 25 mω (room-temperature rating) power JFET characterized up to 250 °C, and a module capable of 1200 V, 120 A DC performance at 25 °C.
    No preview · Article · Jan 2010
  • [Show abstract] [Hide abstract]
    ABSTRACT: A practical parameter extraction procedure for power junction field effect transistor (JFET) is presented. The carrier mobility and carrier concentrations are very important parameters, strongly affecting the current capability and dynamic characteristics of the device for a given design. When modeling JFETs, values of these parameters usually are based on assumptions and given by a vendor in a range. As a result, model accuracy is compromised. In this paper, a step-by-step parameter extraction procedure is described that includes extraction of the mobility and the carrier concentration in the channel and drift regions based on knowledge of the device geometrical parameters. For the first time, carrier mobility in channel and drift regions of power JFET are extracted individually. It is found that channel and drift region mobilities can be very different for a given device, since they are strongly fabrication-process dependent. The developed procedure includes extraction of parameters for proposed empirical temperature dependencies of mobilities in the channel and drift regions. A simple static I-V characterization and C-V measurements are the only measurements required for the parameter extraction.
    No preview · Conference Paper · Oct 2009
  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel SiC junction field effect transistor (JFET) model is proposed that uses a unified description of linear and saturated conduction modes. Advantages of the proposed model are improved robustness and convergence, inclusion of field-dependent mobility effects, and more physical description of the current saturation phenomenon. The model is validated against a normally-off JFET sample over a wide temperature range. Finite element simulation are used to demonstrate the physics-based nature of the proposed model.
    No preview · Conference Paper · Oct 2009
  • D.C. Sheridan · A. Ritenour · V. Bondarenko · P. Burks · J.B. Casady
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    ABSTRACT: Twenty amp normally-off enhancement mode 4H-SiC VJFETs are demonstrated with 1.9 kV avalanche breakdown voltage and a specific on-resistance of 2.8 mOmega-cm<sup>2</sup>. The VJFETs shown near ideal subthreshold characteristics and maintain enhancement mode functionality to temperatures exceeding 175degC due to the optimized channel design with low DIBL characteristics. The low specific on-resistance enables the VJFET to have low intrinsic capacitances that result in low total switching times of less than 150 ns at 15 A at a Tj = 175degC, and low total switching energies of 97 muJ when switching 12 A at Tj = 25degC. Short circuit performance was also investigated with the VJFET exhibiting a rugged short circuit withstand capability in excess of 700 mus at a V<sub>DS</sub> = 600 V.
    No preview · Conference Paper · Jul 2009

Publication Stats

514 Citations
17.90 Total Impact Points

Institutions

  • 2014
    • North Carolina State University
      Raleigh, North Carolina, United States
  • 2000-2005
    • Auburn University
      • Department of Electrical & Computer Engineering
      AUO, Alabama, United States
  • 2002
    • Princeton University
      Princeton, New Jersey, United States
  • 1997-1998
    • Northrop Grumman
      Falls Church, Virginia, United States